This application claims priority from German Patent Application No. 101 50 819.0, filed Oct. 15, 2001.
The invention relates to an energy administration device for operating an absorption refrigerating device using different energy sources, an absorption refrigerating device in particular, which is intended for installation in a living van, caravan or the like. Furthermore, the invention pertains to an absorption refrigerator comprising an energy administration device for operation with different energy sources and being provided for being installed in living vans, caravans or the like in particular.
From DE 31 33 686 C2 an absorber refrigerating unit of a refrigerator for touring caravan and the like, which can be operated using an AC source, a DC source or a liquid gas source. For this purpose the absorber refrigerating device can be automatically switched by means of an electric circuit comprising a plurality of switches and relays. In particular, in this circuit it is detected when during operation with AC current or DC current the voltage drops below a given value and subsequently switching is effected to another energy operation mode. The gas operation system of said absorber refrigerating device comprises a surveillance system using a thermal switch, since using said thermal switch extinction of gas flame is detected and a valve is selected which interrupts gas supply. In this manner of accident survey it is disadvantageous that said thermal switch has a very long response time of 30 to 60 second so that accidents can be detected with long temporal delay only, this impairing safety of the system.
From U.S. Pat. No. 4,656,821 a gas-operated absorption refrigerator is known whose gas supply is regulated via a magnetically controllable valve. This device in the are of the ignition device for the gas burner comprises a thermal element surveying the flame of the burner and selecting an xe2x80x9celectrically selectable valvexe2x80x9d for interrupting of the gas supply, when the flame of the burner is extinguished. In addition, a second sensor is provided for which is coupled to a time switch device and surveys the ignition process of the gas flame. It is guaranteed by this sensor in particular, that the ignition process is not repeated immediately after ignition failed. This system also only comprises thermal elements having a comparatively long response time, for surveillance of the gas flame.
It is, therefore, the main object of the present invention to improve safety of the gas operation in an energy administration device of an absorber refrigerator and to achieve a more accurate control of the entire system.
This object is achieved by the energy administration device as defined in claim 1 as well as by the absorption refrigerator as defined in claim 14.
The energy administration device in accordance with the present invention permit operation of an absorption refrigerating unit with different energy sources and for this purpose comprises an energy control unit for controlling and selecting the energy sources. In addition, said device includes a gas operation unit for operating said absorption refrigerating device with gas, said gas operation unit comprises a burner connected to a gas supply line and being controllable using an ignition surveillance system. The invention is characterized in that said ignition surveillance system comprises an ionisation sensor and/or UV sensor for surveying the gas flame of said gas burner. The use of such sensors is known per se from gas-firing machines, however, never before its use was proposed in energy administration systems for absorber refrigerators.
In case of surveillance using ionisation sensors AC voltage is applied between the sensor electrode and said gas burner mass. The flame rectifies the voltage and said DC signal is recognized by said energy administration device. As compared thereto, in UV surveillance an UV sensor is used which essentially consists of a UV-sensitive tube and electronic components. Only in case of UV radiation generated by the gas flame of said burner the tube switches through. Through switching of the tube also is detected by said energy administration device. In said energy administration device in accordance with the present invention it is an essential advantage that surveillance using ionisation sensors or UV sensors, respectively, very accurately and almost without delay can detect failure of said gas flame. Therefore, an accident in gas operation can be detected much faster and as corresponding consequence gas supply can be interrupted. Thereby, an essentially more accurate control of the device and an improved safety in gas operation is guaranteed.
In a preferred embodiment said ionisation sensor is integrated into the ignition electrode of said gas burner. This permits a compact construction of said gas operation unit.
In a further embodiment the gas supply line comprises a valve electrically selectable by pulse width modulation, which interrupts gas supply when said absorption unit is not operated using gas or when, respectively, an accident is detected in said energy control unit. In case of control of the electrically selectable valve using pulse width modulation, at first an impulse is issued for opening said gas supply line for attracting said valve, and subsequently the voltage is reduced by pulse width modulation. This provides the advantage that the electric energy supply during gas operation is kept very low.
In another preferred embodiment said device comprises an AC operating unit for operation of an absorption refrigerating device with power supply, 230 V power supply in particular. Furthermore, in a particularly preferred embodiment in addition a DC operating unit for operating said refrigerating unit with DC voltage, 12 V DC voltage in particular, is provided for.
For automatic switching to different energy sources in a further embodiment of the present invention an undervoltage detection unit is provided for which is coupled to said energy control unit and said AC voltage operation unit in such manner that said energy control system selects said AC operation when said undervoltage detection unit detects a voltage above a threshold value and said energy control system switches to gas operation or DC operation, when said undervoltage detection unit detects a voltage below said threshold value. Hereby it is guaranteed that said system in case of switching off of power supply automatically is operated using another energy source. The DC voltage operating unit of said system preferably is located in said generator operation unit, the dynamo of the vehicle in particular, in which said absorption refrigerating unit is disposed.
The DC voltage operating unit 1 furthermore also can include a battery and/or solar operating unit. This permits operation by means of DC, also when the generator of the DC voltage operating unit is switched off.
In case the system comprises a DC operation unit, a DC detection means is provided for in a preferred embodiment, which is coupled to said energy control system so that said energy control system selects the DC operation when DC is detected, and another energy operation is selected when no or very low, respectively, DC current is detected. Herein switching to another kind of energy is guaranteed when the DC current of the system fails, e.g. when the generator of the system is switched off.
For controlling the optimum energy output, in a preferred embodiment of the present invention a temperature sensor, an NTC sensor in particular, is provided for arrangement in the refrigerator of said absorption refrigerating device, wherein said temperature sensor is connected to said energy control device and the different kinds of energy operation are controllable by means of the temperature detected by the sensor.
Beside the automatic energy operation control, in a further embodiment of the present invention in addition a possibility of manual change is given, which permits manual change to the different kinds of energy operation. Said energy control device preferably is an electronic control comprising hardware components which are controllable by a software. Furthermore, preferably an operating and display panel is provided for which displays for the user the presently selected kind of energy operation as well as the cooling temperature and permit manual selection of kind of energy operation.